Here is a working 286 motherboard with a 12 MHz CPU and 1MB of RAM which I just pulled from a working 1992 desktop system which was used for voicemail.
This motherboard fits an older AT or Baby AT case. The keyboard connector is the larger DIN5. There are no onboard controllers or I/O ports.
This motherboard was made by Biostar with a Chips and Technologies SCAT chipset (Single Chip Advanced Technology) This single chip supports shadow memory and LIM 4.0 Expanded memory. (If you have studied this historically important chipset, then you and Ella Fitzgerald fans could be called scatologists.)
DIPP chips can be inserted for 512KB, 640KB or 1MB of RAM. This board also uses the short-lived memory modules known as SIPPs (single inline pin packages) for 1MB, 2MB, or a Maximum of 4MB. SIPPs must be installed in pairs. There is currently one pair of SIPPs providing 1MB of RAM.
You can read further details about this motherboard at this have seen this motherboard boot consistently from floppy and from an IDE hard disk.
Miraculously, the 3.6V blue barrel-shaped battery has not leaked at all and still appears to work. It kept the date and the hard drive type while this system was in storage for at least the last decade.
I welcome questions from interested buyers before your purchase. Buyer will receive the exact motherboard, CPU and RAM pictured here, but no documentation, drivers or other softwareI offer a 30 day return privilege and free shipping to any U.S. zip code.